can have a dramatic effect on appearance. For
example, consider the sphere and cone below.
The colours we see in the real
world are based on the interaction between the object materials and the
lighting in the scene.
Using OpenGL, the programmer can
mimic this process using mathematical models for lighting and materials. The result is
that is, varying levels of brightness and darkness that depict depth.
In the real world, shading results
from a multitude of complex interactions, including multiple reflections
resulting from interactions amongst surfaces.